1. Field of the Invention
The present invention relates to a microwave oven, and a method of controlling the same, which performs a cooking operation using a humidity sensor.
2. Description of the Related Art
Generally, microwave ovens perform cooking operations with the aid of atmospheric sensors, such as a humidity sensor, a temperature sensor and a gas sensor, and a weight sensor to measure a weight of food.
Where a cooking is performed according to cooking conditions, a humidity sensor employed in a microwave oven measures water vapor in a cooking chamber. The humidity value measured by the humidity sensor varies as time elapses after the cooking is initiated. That is, as shown in FIG. 1, where food is heated by microwaves of the microwave oven, the amount of water vapor generated during an initial period is small, as compared to the later period of time where the cooking continues.
The humidity value of the humidity sensor varies according to cooking states. Accordingly, it is possible to recognize a completion degree of the cooking by measuring the variation of the humidity value. Furthermore, it is possible to automatically finish the cooking based on the result measured by the humidity sensor.
For ease of understanding, technologies relating to the above operations are described with reference to FIG. 2.
A humidity sensor measures water vapor in a cooking chamber as a cooking operation is performed. Whenever a cooking time has reached respective preset measurement periods of the humidity sensor, while humidity values measured by the humidity sensor are scanned, the humidity values of the humidity sensor obtained by the scanning are accumulated. Generally, an accumulated humidity value corresponding to the scanned humidity values increases as a cooking time elapses. Referring to FIG. 2, a first cooking time T1 to have the accumulated humidity value reach a predetermined value is calculated, and a second cooking time T2 required to perform a further cooking is calculated based on the first cooking time T1. The second cooking time T2 may be different depending on the respective weights and cooking menus (warming, thawing, etc.) set for foods. Accordingly, it is difficult to uniformly set the second cooking time T2. Therefore, in a conventional method/microwave oven, pieces of information of respective cooking times are drawn as a table and pre-stored in the microwave oven, and a second cooking time corresponding to a first cooking time, which is calculated during a cooking, is searched for in the table and obtained.
A further cooking is a process executed until the cooking is finished after the first cooking time T1 is found using the humidity sensor. After the second cooking time T2 has elapsed, a heating device such as a magnetron in operation is turned off, and thus the cooking is automatically finished.
However, in the conventional microwave oven, a measurement period of the humidity sensor may be too long relative to the second cooking time T2 for certain types of food. That is, for some food, the second cooking time T2 should be short and may only require a brief further cooking. In such a case, the food may be overcooked as the microwave oven continues to heat the food while determining the first cooking time T1. For example, where a cooking condition such as a “cooking popcorn” or “warming vegetables” is set, a lot of heat is not required to finish a cooking operation thereof after the food starts to produce steam. Therefore, the cooking operation must be finished within a few seconds after the first cooking time T1. However, because the measurement period of the humidity sensor is long, the cooking operation may not be finished at an appropriate time. Thus, the food is excessively overcooked.